/*
 * Copyright (c) 2014, marco.tamburelli@gmail.com
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met: 
 * 
 * 1. Redistributions of source code must retain the above copyright notice, this
 *    list of conditions and the following disclaimer. 
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution. 
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package org.omorphdb.core.io;

import java.io.File;
import java.io.IOException;

/**
 * Wraps a resources, local (a local file) or remote (a file located to a remote
 * machine) and provided methods to access that resource.
 * 
 * @author Marco Tamburelli
 */
public abstract class Resource
{
	/**
	 * Creates and returns a {@link Reader} of the resource.
	 * 
	 * @return
	 * @throws IOException
	 */
	public abstract Reader createReader() throws IOException;

	/**
	 * Creates and returns a {@link Writer} of the resource.
	 * 
	 * @return
	 * @throws IOException
	 */
	public abstract Writer createWriter() throws IOException;

	/**
	 * Creates and returns a {@link Appender} of the resource.
	 * 
	 * <br>
	 * Note that having an appender also enable to control the resource length.
	 * In fact without a valid appender when the application will terminates,
	 * the file will be terminated where the last page terminates, which can be
	 * much more then the expected file length.
	 * 
	 * @return
	 * @throws IOException
	 */
	public abstract Appender createAppender() throws IOException;

	/**
	 * Returns the position where a new append operation should take place.
	 * 
	 * @return
	 */
	public abstract long getResourceLimit();

	/**
	 * Attempts to remove the current resource. Once removed a resource will
	 * loose all its contents.
	 * 
	 * @return <code>true</code> in case of success.
	 * @throws IOException
	 */
	public abstract boolean remove() throws IOException;

	/**
	 * Creates a {@link Resource} pointing to a local file.
	 * 
	 * @param file The local resource to read/write/append low level
	 *        information.
	 * @param pageSize The size of each page. Used create memory map from file
	 *        where to read and write.
	 * @return
	 * @throws IOException
	 */
	public static Resource create(File file, int pageSize) throws IOException
	{
		return new LocalResource(file, pageSize);
	}
}
